Because it has been known recently that sugars are involved in physiological functions, the studies on sugars are actively promoted. Also, oligosaccharides having a variety of activities have been known, including those of lower cariosity, those having a function capable of normalizing enterobacteria, those having bacteriostatic action, or those having inclusion activity such as cyclodextrin. Such oligosaccharides have made contributions to food industry and the like.
Although some oligosaccharides are directly produced as fermentation products, a great number of oligosaccharides are generally produced through polysaccharide degradation. Conventional process of degrading polysaccharide has been performed enzymatically in aqueous medium or with acid hydrolysis.
However, a great number of the oligosaccharides produced by enzymatic degradation in aqueous media are of lower molecules of nearly dimer to hexamer, particularly dimer or trimer. The yield of an oligosaccharide of a higher polymerization degree than those described above especially 10 or more is low, so the production thereof at a higher efficiency is generally hard.
Oligosaccharides of a lower polymerization degree are for use in low-calory sweeteners or sweeteners of low cariosity. Alternatively, it is said that those of a higher polymerization degree may have a function to increase useful enterobacteria such as Lactobacillus bifidus and the like. However, because oligosaccharides of a higher polymerization degree are produced with difficulty, their studies have not made any advance. Therefore, oligosaccharides of a higher polymerization degree or the process of producing the same have been expected strongly.
In starch industry, pullulanase is used in combination with a variety of amylases so as to improve the yield of glucose and maltose. However, it has never been known the use of pullulanase for the generation of an oligosaccharide of a higher polymerization degree.
From the respect described above, the present invention has been carried out for the object to produce an oligosaccharide of a higher polymerization degree at a higher efficiency and to provide a method of producing an oligosaccharide of a higher polymerization degree through enzymatic degradation, by using polysaccharide as a raw material.